The Azure SQL Database Offline Migration Wizard - does it disable my source db when i start migration

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The Azure SQL Database Offline Migration Wizard - does it disable my source db when i start migration

Mark Taylor 351

I have SQL server on Azure VM. I have setup the azure database migration services. I am on the last step of the wizard where it says in the documentation downtime starts when I hit start migration.

Does it mean that it will destroy, or put the source sql server readonly or offline somehow? Does it simply mean that my application will need reconfiguring to point to the new copy of the database, so for consistency, stop writing to the source database?

I want to test, so I would like the migration to copy the database over so I can use a test copy of the application on the migrated data. When I am satisfied, I aim to cease connections to the source database, complete the migration, reconfigure the application so it runs on the new Azure SQL database.

Should I be doing this another way? I cannot quite read in the documentation what is happening.

Mahesh Kurva 6,850 Reputation points Microsoft External Staff Moderator

2025-08-07T03:40:22.8666667+00:00

Hi Mark Taylor,

We haven’t heard from you on the last response and was just checking back to see if you have a resolution yet. In case if you have any resolution please do share that same with the community as it can be helpful to others. Otherwise, will respond with more details and we will try to help.

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Mahesh Kurva 6,850 Reputation points Microsoft External Staff Moderator

2025-08-07T03:40:22.8666667+00:00

Hi Mark Taylor,

We haven’t heard from you on the last response and was just checking back to see if you have a resolution yet. In case if you have any resolution please do share that same with the community as it can be helpful to others. Otherwise, will respond with more details and we will try to help.

Answer 1

Hi Mark Taylor,

Greetings!!

When you start an offline migration using Azure Database Migration Service (DMS):

Your source SQL Server database remains fully operational it is not disabled, set to read-only, or taken offline automatically.

The term “downtime” refers to the period during which you must stop any new data changes (writes) to the source database. This is essential because any changes made after migration starts will not be included, potentially leading to data inconsistencies.

Your plan is solid and aligns with best practices:

Migrate a copy of your database to Azure SQL Database.

Test your application against the migrated copy to ensure functionality and performance.

Once satisfied:

Stop all activity on the source database.

Optionally, re-run the migration to capture any final changes.

Reconfigure your application to point to the new Azure SQL Database.

For more information, please refer the documents:
https://learn.microsoft.com/en-us/azure/dms/faq?utm_source=chatgpt.com#how-can-i-ensure-that-dms-has-migrated-all-the-data-from-the-source-database-to-azure-sql-targets-https://techcommunity.microsoft.com/blog/microsoftdatamigration/introducing-azure-sql-database-offline-migrations-for-the-azure-sql-migration-ex/3655381?utm_source=chatgpt.com

Hope this helps. Do let us know if you any further queries.

If this answers your query, do click Accept Answer and Yes for was this answer helpful. And, if you have any further query do let us know.

Mahesh Kurva 6,850 Reputation points Microsoft External Staff Moderator

2025-08-08T03:04:15.28+00:00

Hi Mark Taylor,

Following up to see if the above answer was helpful. If this answers your query, do click Accept Answer and Yes for was this answer helpful. And, if you have any further query do let us know.
Mark Taylor 351 Reputation points

2025-08-08T07:06:35.82+00:00

I need to try this, thank you.
Does the migration stay active in the project, so i can re-run subsequently? OR do I have to rebuild and step through the wizard again?For instance, copying the data over as per guidance, testing it works on the pre-production application, once all is well, take live app offline and re-run the migration and go-live.I think I will still lab it to be sure.

Thanks for the documetation links - I missed the schema pre-req, so will check it all again.

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The Azure SQL Database Offline Migration Wizard - does it disable my source db when i start migration

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